1. Field
The following description relates to an in-wheel actuator applicable to a vehicle, such as an electric automobile, which is driven with electrical power, and an in-wheel assembly comprising the same.
2. Description of the Related Art
Hybrid vehicles and electric vehicles have gained more popularity due to harmful environmental effects from air pollution and a shortage of fossil fuels. A hybrid vehicle uses an internal-combustion engine to generate power and uses an electric motor as an auxiliary power source. An electric vehicle uses an electric motor as a main power source.
With the development of technologies for batteries and motors, it is expected that electric vehicles, known as pollution-free cars, replace for “transition” vehicles, such as hybrid cars, since electric vehicles emit no pollutants or carbon dioxide during driving.
An in-wheel system has a driving motor mounted on a wheel, and delivers power from the driving motor directly to the wheel. The application of the in-wheel system allows a vehicle to have a compact and organized driving system, thereby reducing vehicle weight and improving a degree of freedom in vehicle layout or design. In addition, the in-wheel system contributes to optimization of a vehicle frame to increase collision safety. Further, the in-wheel system increases a drive motor performance of the vehicle and facilitates a larger interior space by optimally balancing weight across the vehicle.
In addition, the size of a driving motor is proportional to a level of output torque. Therefore, the bigger the size of the driving motor is, the higher the output torque can be achieved. However, a break and a bearing supporting a hub are installed inside of a wheel of an in-wheel assembly, and a driving motor is installed in the rest of the inside of the wheel. Therefore, the driving motor needs to be thin to prevent interruption from a vehicle body. However, there is a limit to reducing the size of the driving motor, since a high output torque is required to drive a vehicle.
In order to generate high output torque and reduce the size of a driving motor, a decelerator may be installed in an output shaft of a driving motor so as to increase output torque, so that both the decelerator and the driving motor are installed inside of the wheel. In this case, if the driving motor and the decelerator are not arranged compactly or a load is unstably transferred, it may lead to an interruption between the vehicle body and the in-wheel assembly or malfunctions, e.g., vibration or fatigue fracture.